The epithelium of the alveolar region of the lung is susceptible to injury, such as that induced by air-borne toxicants or oxidant stress. Interruption/delay of the replacement of these cells following injury results in faulty repair and irreversibly impaired function in the alveolus. In this proposal, we will show that there exists a critical, dynamic relationship between lung epithelial cells and fibroblasts that dictate their responsiveness to and expression of sulfated extracellular matrices (SECMs) and growth factors. This constitutes a dynamic barrier, modified by the cells themselves, that defines their selective division of labor, maximizes their common efficiency, and is reflected in specific counter-regulation of expression of these modulatory factors. The hypothesis to be addressed is: The sulfated extracellular matrix between alveolar epithelium and underlying fibroblasts selectively down-regulates generation and activity of key regulatory factors: FGF-1, -2, and -7, and their adaptor molecules (FGF-receptors, FGF-binding protein, and specific sulfated ECMs). These processes constitute critical paracrine and juxtacrine mechanisms for regulating cell numbers, cell functions, and cellular architectural arrangement under normal, hyperplastic, and disease states in the alveolus. Isolated AT2 cells will be co-cultured with fibroblasts and the intervening sulfated ECM environment modified by either exogenous addition or stimulated overproduction (enhancement) or selective inhibition/modification of gene/protein expression (reduction). To define the mechanisms that control critical epithelial cell-fibroblast interactions, cellular responses to over expression of key regulatory growth factors and inhibited translation of growth factor response adapters will be measured by DNA synthesis, relevant signaling events, and expression of selected gene/protein products. Whole animal studies using adenovector-mediated gene transfer will determine if over expression of FGF-BP or syndecan-1 improves or alters injury/repair outcomes in an in vivo model of pulmonary fibrosis. Results of these studies are expected to provide essential information needed to better understand basic cell-cell, celI-ECM relationships in homeostasis, as well as the mechanisms that steer the pathogenesis of fibrogenic change in the lung because of injury and/or disease. [unreadable] [unreadable]